This application incorporates by reference related patents U.S. Pat. Nos. 6,022,201; 3,153,984; and 2,589,449, and, GB Patent No. 1,000,591 each in their entirety.
Early devices to vary the displacement of vane pumps involved the deliberate offset of the rotational center of the vane rotor with respect to the geometrical center of the circular outer case. The amount of offset would then control the swept volume of the pump and thereby provide a desired volumetric output for each rotation of the rotor. Several problems with this design limited its use.
First, the pressure unbalance caused by the hydraulic-based force on the radial cross-section of the rotor and vanes at the axis viewed from the radial perspective severely limited the power capability and power density of these pumps and resulted in very heavy, inefficient, and cumbersome devices. Second, the centrifugal force of each vane during high-speed rotation caused severe wear of the vane outer edge and the inner surface of the outer containment housing.
Later fixed displacement design were conceived around the concept of pressure balance in which two geometrically opposed high pressure chambers would cause a cancellation of radial load due to equal and opposed cross-section pressure areas and opposite vector direction which resulted in a zero net force radially on the shaft bearing. The design is referred to as the pressure balanced vane pump or motor. Typical efficiency of these devices is 70 to 85% under rated loading and speed. Still later improvements include changing the chamber shape of pressure balanced vane style devices and involved the use of several types of adjustable inner surfaces of the outer housing for guiding and radially adjusting the vanes as they rotate. One improvement is a continuous band, which is flexible and subject to radial deformation so as to cause displacement control of the vanes. However, these flexible bands did not rotate.
Classical freon heat pumps utilize an expansion valve to rarify the freon and drop its temperature to xe2x88x9240xc2x0 F. The expansion valve represents a large loss of mechanical energy relative to the overall system performance due to shear heating effects as the fluid is discharged through the valve. In spite of that, common recoveries or amplifications of the electrical energy input to drive the system is achieved by as high as 300%. Nevertheless, improvements reducing the mechanical loss would certainly result in greater efficiency.
The basic embodiment of this invention is a rotor with spring-biased, radially extensible vanes that are constrained in their outward radial movement, away from the rotor center of rotation, by the inner circumferential area of a continuous flexible band that has the same axial width as the rotor and vanes. It is especially important to notice in the basic embodiment that the flexible band is designed to rotate with the vanes and rotor. The spring loading of the vanes is by conventional means as is the practice with existing vane pumps and motors; namely that the spring is compressed between the rotor itself and the radially inward edge of the vane so as to drive every vane radially out from the rotor body against the inner area of the flexible band. Other spring assemblies that accomplish the same function are also contemplated. The spring preload causes the vanes to contact the flexible band inside surface at slow speeds that include zero. This is especially important if this embodiment is to be used as a variable or fixed displacement hydraulic motor because hydraulic sealing of the vane""s outer edge is assured at zero speed. Since the flexible band is totally free to rotate with the vanes and rotor, a very big source of friction, wear, and inefficiency is eliminated due to the teaching of this invention. The well known limitation of the prior art; namely the sliding edge friction associated with the combined outward radial force of the vanes is totally eliminated since there is substantially no relative motion between outside edges of the vanes and the interior constraining surface of the flexible containment band. Further, as the rotor""s speed increases, the speed-squared radially outward combined force of the set of vanes is fully contained by the continuity of the flexible band simulating a pressure-vessel type of containment, as if the flexible band were a cross section of a pressure containment cylinder, and the individual radial outward force of the vanes were the pictorial radially outward arrows that are used in drawings to depict the action of the force which is contained. Since the action of the flexible band is to fully contain these combined radial forces of the vanes, there is absolutely no increase of frictional forces due to increasing radial vane force, and this invention solves a very severe limitation of the prior art in that the rotating speed of the fixed devices built according to the prior art is limited to about 4,000 revolutions per minute, while the upper speed limit of the subject invention is substantially higher, say to the range of 30,000 revolutions per minute, governed largely by the design strength and durability of the flexible band. In fact, testing showed that the efficiency of this invention utilizing the rotating components of a commercially available pump having an advertised efficiency of 88% resulted in efficiency measurements of 93.5 to 94.7% when used in combination with the rotating flexible band. The greater efficiency of the instant invention over the prior art will result in much smaller variable pumps and motors in severe applications such as spacecraft. The flexible band design and construction can cover a wide range of variables, from a single circumferentially continuous flexible band to concentric nesting of any practical number of individual circumferentially continuous flexible bands. The smallest circumference band is concentrically nested within a slightly larger second band and the second band is concentrically nested within a still larger inside circumference of a third and yet larger band, and so on, up to the largest outside band whose exterior surface is the exterior surface of the nest and the smallest inner band has its interior surface in contact with the exterior edge of each of the vanes. The construction is similar to the case of a stranded cable of a specific diameter having a much greater strength than a solid rod of the same diameter. Also, the stranded cable is more flexible without failure than the solid rod. The individual clearances between each of the bands in such a collective nest can be chosen to allow slippage and lubrication from one band to the next. This nested band-to-band clearance results in a greater efficiency at very high operating speed by allowing a nested concentric set of bands to slip in speed from one concentric member to the next, with the inner band rotating at substantially the same speed as the rotor and the outer bands rotating increasingly slower. The material used to make the endless flexible band can be any appropriate metal, but other appropriate materials, such as plastic, fiberglass, carbon fiber, or KEVLAR(copyright), can be used. This construction material range applies whether a single thickness endless band is constructed, or a concentric nesting of two or more bands is used to make a concentric nesting of a number of bands. The description thus far is of a flexible circular and continuous containment band with the band confining all the radial centrifugal forces of vanes and eliminating contemporary problems such as sliding vane friction, the speed-squared frictional dependence, and the rotor speed limitation. The flexible band construction will also allow for the shape manipulation of the circumference of the band so as to permit varying the swept chamber volume as the rotor turns.
Reshaping of the flexible band is necessary to control the swept chamber volume of the pump as the rotor is turning and comprises an array of radially moveable pistons which are at 0xc2x0, 90xc2x0, 180xc2x0, and 270xc2x0 around a full circle, i.e., at 12 o""clock, 3 o""clock, 6 o""clock, and 9 o""clock of a clock face. Each of the pistons has an appropriate curvature to contact the flexible band external surface in the positions cited. If the 12 o""clock and 6 o""clock pistons are caused to move inward, the fixed circumference of the flexible band tends to cause the 3 o""clock and 9 o""clock pistons to move outward by an equal amount, but the flexible nature of the containment band permits unequal piston motion. The inward or outward movement of the pistons may be driven by individual controlled hydraulic pressure, or the movement can be caused by mechanical means such as a gear and rack, or radially disposed screw drives to each piston. Another type of piston control means would be the joining of an analog type electric servo motor drive to a ball screw mechanism with an encoder position feedback; which arrangement would easily lend itself to digital control. Whatever the method of controlling the movement of the piston, the final purpose is to controllably elliptasize the flexible band from an axial perspective so as to cause the controlled and varying degrees of swept volume of fluid flow per revolution of the vane pump or motor. In the basic embodiment of this invention, opposing pairs of pistons move simultaneously towards or away from each other, while the remaining set of opposed pistons behave in simultaneous opposition to the action of the first pair. This behavior results in varying degrees of elliptic reshaping of the flexible band viewed from the axial perspective of the vane rotor. A novel and significant aspect of this device is the freedom of movement of the flexible band, which is impossible in the prior art. This includes a special manipulation of the pistons and band that allow the combination of this invention to simultaneously manipulate two common fluids, but hydraulically separate, outputs of this device as pump or motor. The variable pressure balanced design has two equal and identical pressure fluid outputs which will be merged so as to drive a hydraulic motor to form what is called a hydrostatic transmission. This is a second embodiment of the present invention. In addition, a second variable vane device of the proposed design may act as a motor in a conventional type of hydrostatic transmission with all of the current results, but with much greater efficiency and range. Another embodiment of the invention is a special piston manipulation that causes this invention to act like the early variable non-pressure balanced construction pumps with a single input and output. In the present invention, there is shown two separate hydraulic circuits with separate inputs and outputs where a single pump of the proposed design is separately connected to two fixed displacements hydraulic motors. Motor Number 1 will connect in closed hydrostatic loop with the first and second quadrant ports of the pump, while motor Number 2 will connect in closed hydrostatic loop to the third and forth quadrants with no interconnection. The plumbing of the motor circuits would be such that both motors would have the correct shaft rotation direction for a hypothetical example, say forward. If the 12 o""clock and 6 o""clock pistons were directed inward, the 3 o""clock and 9 o""clock pistons would be forced outward with equal hydraulic flow to both motors occurring, causing the motors to turn at the same controlled speed in the forward direction. Now assume that the original circular flexible band shape is modified such that the 3 o""clock piston is moved inward and the 9 o""clock piston is moved outward, while holding the 12 o""clock and 6 o""clock pistons at neutral, the band remaining circular in shape. A first motor connected to the first and second quadrants will reverse shaft directions, with a speed equal to that of a second motor whose direction is still forward. If the 3 o""clock and 9 o""clock piston were both moved the other way, the second motor would instead reverse rotation in relation to the first motor. Combine this action with the original action of the basic embodiment as described, and one motor can be caused to rotate deliberately and controllably faster than the other motor, such as is the case for an axle set of a vehicle going around a turn. Another embodiment of the invention has two separate piston control methods which can be algebraically mixed to effect differential control means of axle rotation for negotiating a turning radius. Another embodiment comprises a fixed displacement motor of the prior art constructed in the manner of this invention, with the pistons permanently fixed. This arrangement will be much more efficient than conventional hydraulic motors. A still further embodiment is the case of fixed displacement motors and pumps which can greatly improve the efficiency of existing vane pump and motors; namely that one or several flexible bands of the proposed invention construction can be closely fitted to be movable just inside the fixed elliptic or circular cam ring surface of conventional units, with a small clearance between the flexible ring exterior and the fixed cam ring interior, said clearance supporting an oil film which has minimal friction, while the vane outer edges are now supported by the innermost flexible band""s inner surface. This construction provides some of the advantages of the subject invention, such as containment of vane centripetal force, and the replacement of vane-to-fixed cam ring friction with broad oil film friction that is much less, and not speed squared dependent. The primary invention configured as a fixed unit will still be most efficient due to the open chamber between each fixed piston pair. A smaller total oil film in this case will give the least loss. A significant advantage of the just described construction is the ability to fix existing design, or even retrofit field product without any mechanical change required. Existing vane units could compete with fixed piston pumps and motors in terms of efficiency, but would be less efficient than the basic embodiment. This is a fifth embodiment of the invention.
Finally, in yet another aspect of the invention, the hydraulic vane pump with a flexible band control described in U.S. Pat. No. 6,022,201, also known as an hydristor, may be employed in a heat pump system characterized as a hydristor heat pump. The hydristor heat pump preferably contains a closed freon loop containing a first and a second closed half loop, the hydristor being integral to the closed freon loop and in fluid communication therewith. A first half of the hydristor contains at least one kidney port forming a first inlet (e.g., in the fourth quadrant as shown in FIG. 4) and at least one kidney port forming a first outlet (e.g., in the first quadrant as shown in FIG. 4). The first half of the hydristor functions as a pump/compressor as a chamber rotatably communicating with the rotor is volumetrically reduced as it rotates from the fourth quadrant to the first quadrant. The volumetric compression of the chamber in turn compresses the compressible fluid or freon contained therein through the first inlet chamber, and as such results in a heated liquid stream exiting the first outlet into the second closed half loop.
The heated liquid freon stream then enters a second heat exchanger connected inline to the second closed half loop and thereby transfers heat to a cold reservoir such as a home heating system or a Stirling engine. The cooler freon stream exiting the second heat exchanger then continues in the second closed half loop back to a second half of the hydristor.
The second half of the hydristor contains at least one kidney port forming a second inlet (e.g. in the second quadrant as shown in FIG. 4) and at least one kidney port forming a second outlet (e.g. in the third quadrant as shown in FIG. 4). The cooler freon stream enters the second inlet and exits the second half of the hydristor through the second outlet as a cooled and expanded gas freon stream. The second half of the hydristor functions as a motor/expander as the chamber rotatably communicating with the rotor is volumetrically increased as it rotates from the second quadrant to the third quadrant, and to the fourth quadrant as well. The volumetric expansion of the chamber in turn expands the compressible fluid or freon contained therein through the first inlet chamber, and as such results in a rarified gas freon stream exiting the second outlet into the first closed half loop at low pressure and temperature.
The rarified gas freon stream then enters a first heat exchanger connected inline to or integral with the first closed half loop and thereby absorbs heat provided from a relatively warm reservoir such as the ambient air. The warmer rarified gas freon stream then exits the first heat exchanger and continues in the first closed half loop back to the first inlet for completion of a pump cycle. Note that quadrant four also increases volume and therefore creates additional motor torque thereby further reducing power input to the motor. The increased efficiency of the hydristor results in a reduction in the torque required by a startup motor associated with the hydristor heat pump. Furthermore, the increased efficiency of the hydristor actually enables the economic use of a Stirling engine thereby providing the benefits described hereinbelow.
Stated another way, a heat pump system in accordance with the present invention contains a hydristor pump/motor in fluid and thermodynamic communication with a first heat exchanger communicating with a relatively warm reservoir, and a second heat exchanger communicating with a relatively cold reservoir. The hydristor and the first and second heat exchangers are integral to and in fluid communication with a closed compressible fluid loop. A Stirling engine or a home heating system may, for example, utilize heat transferred from the second heat exchanger thereby providing a reduction in energy usage and costs heretofore unrealized
Another advantage is that the freon compressor oil circulates in the entire system and will tend to collect at the contact surfaces between the flexible band outer surface and the curved contact areas of the control pistons to form large hydrodynamic bearings that are self-actualizing hydraulic seals and low friction bearings.